We're talking strings, numbers, arrays and objects serialized and deserialized. Just scroll down for a giant list of encoders and decoders in any language of your choice, of course including ActionScript. JSON is used heavily in AJAX JavaScript (which is ECMAScript compliant, just like ActionScript).

JSON is for 'transfering' information that can be reassembled into number, string, array, object, etc. format afterwards.

Excel can import CSV but it might not understand the complexity of the information. Tyically what you would do is serialize complex information with JSON, recieve it on the other side (wherever that might be) and then deserialize it. After you deserialize it using JSONs abilities to turn your information back into what is was (numbers, strings, arrays and object) it is up to you how you restructure the data for the format you choose.

Your original intent of preserving CSV is best for Excel or OpenOffice Calc. You didn't mention your intent. JSON would package those (CRLF) \n's for you.